#include <bits/stdc++.h>

using namespace std;



struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

class Solution {
public:
    bool helper(TreeNode *l,TreeNode *r){
        if(l==nullptr&&r==nullptr) return true;
        if(l==nullptr||r==nullptr||l->val!=r->val) return false;
        return helper(l->left,r->right) && helper(l->right,r->left);
    }
    bool isSymmetric(TreeNode* root) {
        if(root==nullptr) return true;
        return helper(root->left,root->right);
    }
};

int main(){




    return 0;
}